The present invention relates generally to communication systems and, in particular, to using a pseudo-random signal to determine one or more characteristics of a communication resource within a communication system.
In wireless communication systems today, sending devices are known to transmit to receiving devices pre-defined signals which are known to the receiving devices. Using such signals, receiving devices make signal quality measurements and perform location determination. A receiving device can compare a received signal to an expected signal and, thus, determine the quality of the received signal. Global positioning system (GPS) satellites continuously transmit known signals for the purpose of location determination by receiving devices. Each GPS satellite transmits a pseudo-random signal generated from a unique pseudo-random sequence. Receiving devices, equipped to predict and identify the pseudo-random sequence of each satellite, receive signals from multiple satellites. Location determination of the receiving devices can then be performed based on the location of each satellite and the delay of the received signal from each satellite.
Wireless communication systems such as cellular systems and two-way radio systems have limited communication bandwidth with which to provide multiple communication services to users. Signal quality measurement and location determination are useful capabilities for wireless communication systems in general. Communication units within such systems make signal quality measurements in an attempt to more efficiently utilize the limited communication bandwidth. And the ability of a communication unit to determine its own location is useful particularly in emergency situations. Transmitting known signals to communication units for signal quality measurement or location determination requires a portion of the limited communication bandwidth, however. In communication systems today, therefore, the allocation of limited communication bandwidth to such signals either has the effect of reducing system capacity or degrading communication services in use.
Therefore, a need exists for an apparatus and method that uses signals known to both the sending and receiving devices for such purposes as measuring signal quality and determining location, whereby system capacity is not reduced and communication services are not degraded.